The present invention relates to an electric double layer capacitor and a method of forming the same, and more particularly to an electric double layer capacitor with an improved surface structure of a polarized electrode.
In recent years, there has been required a capacitor having a long life-time and a large energy density for storing an energy generated by an energy source or a solar battery, wherein the capacitor is used in combination with the energy source for driving a motor or the solar battery. An electric double layer capacitor has been developed as such the battery
A first conventional electric double layer capacitor is disclosed in Japanese patent publication No. 2722021. Top and bottom cylindrically-shaped non-conductive rubber sealing members are separated by a porous separator. Inner spaces of the top and bottom cylindrically-shaped non-conductive rubber sealing members are filled with an active carbon paste. To and bottom collectors seal the top and bottom portions of the top and bottom cylindrically-shaped non-conductive rubber sealing members. The active carbon paste electrode has a flat surface. The above Japanese patent publication is silent on any description about surface shape of polarized electrodes.
A second conventional electric double layer capacitor is disclosed in Japanese laid-open patent publication No. 3-124013. Two solid-state polarized electrodes are separated by a separator. The two solid-state polarized electrodes have recessed portions adjacent to opposite surfaces of the separator, wherein the recessed portions extend on center regions of the two solid-state polarized electrodes, thereby forming two inner spaces adjacent to the opposite surfaces of the separator. The two inner spaces are filled with an impregnant which comprises a pasted mixture of an electrolytic solution with active carbon powders or active carbon fibers.
The above described first and second conventional electric double layer capacitors use polymers such as rubbers and plastics as a seating material and a collector material. Under a high temperature condition, the electrolytic solution may transmit through the sealing material and the collector material, whereby an amount of the electrolytic solution in the capacitor is gradually decreased, whereby an ion-conductivity is gradually reduced. The reduction in ion-conductivity results in an increase in internal-resistance of the capacitor. Namely, if the above first and second conventional electric double layer capacitors are placed under a high temperature condition for a long time, then the internal resistance is increased.
In the above circumstances, it had been required to develop a novel electric double layer capacitor free from the above problem.
Accordingly, it is an object of the present invention to provide a novel electric double layer capacitor free from the above problems.
It is a further object of the present invention to provide a novel electric double layer capacitor free of any substantive increase in internal-resistance even if the electric double layer capacitor is placed under a high temperature condition for a long time.
It is a still further object of the present invention to provide a novel surface structure of an polarized electrode in an electric double layer capacitor free from the above problems.
It is yet a further object of the present invention to provide a novel surface structure of an polarized electrode in an electric double layer capacitor free of any substantive increase in internal-resistance even if the electric double layer capacitor is placed under a high temperature condition for a long time.
It is moreover of the present invention to provide a novel method of forming an electric double layer capacitor free from the above problems.
It is still more object of the present invention to provide a novel method of forming an electric double layer capacitor free of any substantive increase in internal-resistance even if the electric double layer capacitor is placed under a high temperature condition for a long time.
The present invention provides an electric double layer capacitor having a pair of poled electrodes separated by a separator, the polarized electrodes having surfaces facing to the separator, wherein substantially entire parts of the surfaces of the polarized electrodes are spaced from the separator to form inner spaces between the polarized electrodes and the separator.
The above and other objects, features and advantages of the present invention will be apparent from the following descriptions.